1. Field of the Invention
The present invention relates to a fuel cell power supply comprising a fuel cell and a capacitor which are connected parallel to each other, and more particularly to the art of controlling the amount of a reacting gas supplied to a fuel cell.
2. Description of the Related Art
Heretofore, there is known a hybrid fuel cell power supply comprising a fuel cell and a capacitor which are connected parallel to each other. When a current demanded by the load of the fuel cell power supply increases sharply, if the fuel cell fails to supply a sufficient output current due to its response delay, then the capacitor discharges a current to make up for the output current shortage. See Japanese laid-open patent publication No. 6-275296, for example, for details.
In the known hybrid fuel cell power supply, the amount of a reacting gas (a reducing gas such as hydrogen or the like which serves as a fuel and/or an oxidizing gas such as air or the like for reacting with the reducing gas to extract electrons) supplied to the fuel cell is controlled depending on a target supply current which is determined based on the current demanded by the load of the fuel cell power supply.
The inventor of the present invention has found that in a hybrid fuel cell power supply comprising a fuel cell and an electric-double-layer capacitor of extremely large electrostatic capacitance which are connected parallel to each other, when the amount of a reacting gas supplied to the fuel cell is controlled depending on a target supply current which is determined based on the current demanded by the load of the fuel cell power supply, a compressor for supplying the reacting gas may operate excessively or the supplied reacting gas may run short because of the response delay of a system for supplying the reacting gas.
If the compressor for supplying the reacting gas operates excessively, then it tends to waste the electric power supplied thereto. If the supplied reacting gas suffers a shortage, then the electrolytic membrane of the fuel cell is liable to deteriorate, resulting in a performance failure of the fuel cell.